I. Field of the Invention
The present invention relates generally to fasteners and, more particularly, to an extendable fastener for a machine table having at least one T slot.
II. Description of the Prior Art
There are many types of machine tables, such as those used with vertical mills, drill presses and the like, which have a work supporting surface on which the work is positioned. In addition, a plurality of inverted T shaped slots or T slots are formed in the table so that the leg or narrower portion of the slot is open to the work supporting surface. Conversely, the cross bar or wider portion of the T slot is positioned below the surface of the table.
In order to clamp the work to the table, it has been the previous practice to slide a T bolt in from one end of the slot on the table and to a position adjacent the work. These previously known T bolts are dimensioned so that, although the T bolt can longitudinally slide along the slot, they cannot rotate within the slot. Consequently, with the T bolt positioned adjacent the work, a clamp or other fastener is secured to the upwardly extending end of the T bolt by a nut or the like. Since the T bolt cannot rotate within the slot, the nut and clamp can be tightened as desired.
A problem arises, however, when a longer T bolt is required and is neither available or presently secured to the machine table. When this occurs, a T bolt extension is used to extend the effective length of the T bolt.
These previously known extensions typically comprise an elongated stud having external threads at at least one end. An internally threaded collar is threaded onto one end of the stud and is also threaded onto the threaded end of the T bolt and the collar is tightened against the T-bolt. In doing so, the effective length of the T bolt is increased.
One disadvantage of these previously known T bolt extensions is that the collar often becomes loosened when the nut used to clamp the workpiece is loosened by the machine operator. When this occurs, the extension for the T bolt assembly must be reassembled before the clamp can be used on another workpiece.
One previous solution to this problem is to provide flats on the extension stud which is engaged by a wrench held by the operator while the nut on the T bolt is loosened. This previously known practice, however, is not only time consuming and oftentimes difficult to achieve, but also in many cases the flats cannot be reached by a wrench.